CN219609328U - Wide-angle short-focus projection lens - Google Patents

Abstract

The utility model discloses a wide-angle short-focus projection lens, which comprises a rear group, a focusing group and a front group, wherein the rear group at least comprises an aspheric lens and a cemented lens; the focusing group at least comprises a group of positive and negative lenses; the front group includes a positive lens group and a negative lens group of large optical power. The utility model has the advantages of large projection breadth, high resolution, good manufacturability, low cost and no virtual focus at high temperature.

Description

Wide-angle short-focus projection lens

Technical Field

The utility model relates to the technical field of projection lenses, in particular to a wide-angle short-focus projection lens.

Background

In recent years, with the rise of entertainment and home theatres, projectors with large projection ranges have good ornamental effects and are favored in the market.

At present, two common modes for realizing a large-breadth projection effect are as follows: the refraction and reflection lens is formed by combining a refraction lens and a reflecting mirror, and the refraction and reflection lens is easy to realize a large breadth, has the defects of containing more aspheric lenses, generally 4-5 lenses, high mold opening cost and relatively sensitive lens assembly tolerance. Another type of conventional lens is a refractive lens with a small projection ratio, typically a wide-angle lens with a reverse distance, and a large projection area is obtained by extending the projection distance, but is easily limited by the space and place.

For example, CN211528810U is a preferred lens structure, focusing is simple, but the following drawbacks exist:

1. the projection ratio is about 1.1, for example, a screen with the size of 100 inches is projected, the projection distance is required to be 2.43 meters, and at the moment, the projector needs to be placed in the middle of a living room, so that space is wasted and walking is influenced;

2. the resolution is insufficient. Patent CN211528810U uses 1080P (1920×1080) resolution, and the graininess is noticeable in a large format. Therefore, it is necessary to design a wide-angle short-focus projection lens.

Disclosure of Invention

Aiming at the situation, in order to overcome the defects of the prior art, the utility model provides the wide-angle short-focus projection lens, which effectively solves the problems of small projection breadth and insufficient resolution.

In order to achieve the above purpose, the present utility model provides the following technical solutions: a wide-angle short-focus projection lens comprises a rear group, a focusing group and a front group; the rear group at least comprises an aspheric lens and a cemented lens, the focusing group at least comprises a positive lens and a negative lens, and the front group comprises a positive lens group and a negative lens group with large focal power.

Preferably, the rear group aspheric lens is a first lens closest to the prism, the cemented lens is a three cemented lens and is close to the diaphragm, the negative lens in the focusing group is close to the diaphragm, the positive lens group with large focal power of the front group is only composed of a plurality of positive lenses, the negative lens group is only composed of a plurality of negative lenses, the positive lens group is close to the focusing group, and the negative lens group is close to the projection surface.

Preferably, in the rear group triple cemented lens, the positive and negative distribution of the lens is: the positive-negative-positive, wherein the negative lens is made of material with high refractive index Nd being more than or equal to 1.83 and low Abbe number Vd being less than or equal to 40, the positive lens is made of material with low refractive index Nd being less than or equal to 1.50 and high Abbe number Vd being more than or equal to 70, at least one lens in the front positive lens group is made of material with high refractive index Nd being more than or equal to 1.83, and at least one lens in the negative lens group is made of material with high Abbe number Vd being more than or equal to 70.

Preferably, the overall focal power of the focusing group is weaker, the absolute value of the focal power is in the range of 0-0.01, the combined focal power of the front group positive lens group is stronger, the absolute value of the focal power is larger than 0.03, the combined focal power of the front group negative lens group is stronger, and the absolute value of the focal power is larger than 0.1.

Preferably, the three cemented lenses in the rear group have a drum-shaped lens with convex outlines on two sides, the positive lens in the focusing group has a meniscus lens with outline on two sides, the front group has at least one biconvex positive lens, the negative lens group has at least one biconcave negative lens and one meniscus negative lens, and the meniscus negative lens is close to the projection surface.

Preferably, the rear group comprises, in order from the object side to the image side: the lens comprises a first aspheric positive lens, and a triple cemented lens formed by a first spherical positive lens, a second spherical negative lens and a third spherical positive lens; the focusing group includes: a diaphragm aperture, a fourth spherical negative lens and a fifth spherical positive lens; the front group includes: a sixth spherical positive lens, a seventh spherical positive lens, an eighth spherical negative lens, a ninth spherical negative lens, and a second aspherical negative lens.

The beneficial effects of the utility model are as follows:

(1) By reasonably using the aspheric lens and the focal power layout, the projection ratio can reach 0.5, and the short-distance large-breadth projection is realized under the condition of ensuring the maximum cost performance.

The back group of the present utility model uses a glass aspheric lens, which bears the main focal power, monochromatic aberration correction and telecentricity optimization of the back group. Because different aperture bands on the surface of the aspherical lens have different R values, the aspherical lens has strong correction capability for monochromatic aberration, especially aperture-dependent aberration such as on-axis spherical aberration and off-axis spherical aberration, and has a cost performance far superior to that of a spherical lens, and meanwhile, in order to reduce lens defocus caused by temperature as much as possible, the aspherical lens is made of glass materials with smaller thermal expansion coefficients. The bonding surface of the positive-negative-positive three-bonding lens of the rear group is provided with a diaphragm and a back diaphragm, and the larger light angle on the bonding surface and the refractive index difference on the two sides can be used for generating rich and diversified higher-order aberration, so that the correction capability for monochromatic aberration is very strong. As for chromatic aberration, a positive lens with a low refractive index and a high abbe number is matched with a negative lens with a high refractive index and a low abbe number, so that better correction can be obtained. The secondary spectrum is relieved by selecting a positive lens material with a specific dispersion coefficient.

And the focusing group consists of a pair of positive and negative lenses. Because the focal length of the lens is basically maintained unchanged during focusing, the focal power of the whole focusing group is weaker. When the focal power is weak, the centering coefficient of the lens is generally smaller, and the lens is not easy to process. Since aberration correction generally requires a combination of positive and negative powers, the use of separate positive and negative lenses is highly advantageous for correction of aberrations. During the movement of the focusing group, the aberration of the central field of view is almost unchanged, and the aperture edge changes relatively greatly.

The positive lens group of the front group consists of two positive lenses, and in view of tolerance issues, it is often possible to split into three positive lenses to share the power, which is not an essential difference. The negative lens group consists of three negative lenses, including two biconcave spherical negative lenses and one meniscus negative lens. The negative meniscus lens is bent to the diaphragm mainly in consideration of large aberration easily caused by overlarge incident angle of the off-axis light beam, so that the light is basically vertically incident on the convex surface of the meniscus lens. The negative focal power of the meniscus lens can reduce the light deflection angle and provide smaller caliber light beams for the subsequent lens. The two biconcave spherical negative lenses and the positive lens group form a field curvature correction system. The negative lens is arranged at the position with smaller caliber of the light beam, the positive lens is arranged at the position with larger caliber, and the light height can be used as a lever to forcefully correct the curvature of field under the condition of smaller sum of total focal power absolute values. In consideration of the problems of large angle of light and tolerance, the negative lens can be added to share the focal power, so that a better mass production effect is realized.

(2) And the back focal distance is enlarged, and the XPR technology is utilized to improve the visual resolution.

The patent CN211528810U uses a physical resolution of only 1920 x 1080, if a piece of plate glass is inserted between the prism and the lens, the plate glass is made to make a periodic reciprocating motion according to a certain inclination angle, so that a light beam can be slightly shifted, if the light beam is sequentially shifted by 0.5 pixel width according to the order of right, lower, left and upper, then by the persistence effect of vision of human eyes, when the light beam shift reaches a certain speed, the visual resolution of 3840 x 2160 can be superimposed in human brain, and the effect of viewing is improved, which is called as XPR technology of DLP.

XPR techniques require a longer back focus to accommodate the galvanometer and avoid structural interference of the galvanometer and the DMD. This increases the difficulty of the lens, but by using an aspherical lens in the rear group, the difficulty of design can be reduced.

Drawings

The accompanying drawings are included to provide a further understanding of the utility model and are incorporated in and constitute a part of this specification, illustrate the utility model and together with the embodiments of the utility model, serve to explain the utility model. In the drawings:

FIG. 1 is a schematic view of a wide-angle short-focus projection lens according to the present utility model;

fig. 2 is a schematic structural diagram of the rear group, the focus group and the front group according to the present utility model, respectively, according to the present utility model 2 (a), 2 (b) and 2 (c);

FIG. 3 is a schematic view of a light path of a projection lens according to the present utility model;

FIG. 4 is a schematic view of an actual scene of light passing through a projection lens of the present utility model;

FIG. 5 is a simulation of the imaging quality of the present utility model, wherein FIGS. 5 (a) and 5 (b) are vertical axis color difference diagrams at the screen for an 81 inch and 238 inch projection screen at 20deg.C, respectively, for a pixel size of 937um for an 81 inch projection screen size and 2744um for a 238 inch projection screen size;

FIG. 6 is a simulation diagram of the imaging quality of the present utility model, wherein FIG. 6 (a) and FIG. 6 (b) are the lateral fan diagrams at the screen when the ultra-short focal projection lens of the present utility model projects images of 81 inches and 238 inches at 20 ℃, respectively, the scale of FIG. 6 (a) is + -2000 um, and the scale of FIG. 6 (b) is + -4000 um;

FIG. 7 is a simulation of the imaging quality of the present utility model, wherein FIGS. 7 (a) and 7 (b) are MTF diagrams at a screen at an ambient temperature of 20℃and 50℃for an 81 inch projection screen, respectively, for an ultra-short focal projection lens of the present utility model, and the MTF observation line pair is 0.536lp/mm for an 81 inch projection screen;

FIG. 8 is a simulation of the imaging quality of the present utility model, wherein FIGS. 8 (a) and 8 (b) are MTF diagrams at a screen at ambient temperatures of 20℃and 50℃for a 238 inch projection screen, respectively, for an ultra-short focal projection lens of the present utility model, and the MTF observation line pair is 0.183lp/mm for a 238 inch projection screen;

reference numerals in the drawings:

100. wide-angle short-focus projection lens

101. Display chip

102. Display chip protective glass

103. Equivalent prism

104. Flat glass of vibrating mirror

110. Rear group

111. First aspheric positive lens

112. First spherical positive lens

113. Second spherical negative lens

114. Third spherical positive lens

120. Focusing group

121. Diaphragm

122. Fourth spherical negative lens

123. Fifth spherical positive lens

130. Front group

131. Sixth spherical positive lens

132. Seventh spherical positive lens

133. Eighth spherical negative lens

134. Ninth spherical negative lens

135. And a second aspheric negative lens.

Detailed Description

Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those of skill in the pertinent art, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present utility model. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

In the description of the present utility model, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings.

Referring to fig. 1-8 (b), which are schematic structural diagrams of a short-focus projection lens according to the present utility model, according to the sequence of light propagation, the short-focus projection lens 100 of the present utility model, where the projection lens 100 includes a display chip 101, a display chip protection glass 102, an equivalent prism 103, a plate glass 104 of a vibrating mirror, a rear group 110, a focusing group 120, and a front group 130; wherein the rear group 110 includes a first aspheric positive lens 111, a first spherical positive lens 112, a second spherical negative lens 113, and a third spherical positive lens 114, and the focusing group 120 includes a diaphragm 121, a fourth spherical negative lens 122, and a fifth spherical positive lens 123; the front group includes a sixth spherical positive lens 131, a seventh spherical positive lens 132, an eighth spherical negative lens 133, a ninth spherical negative lens 134, and a second aspherical negative lens 135.

The chip 101 of the present utility model is generally referred to as a digital micromirror array (DMD).

Referring to fig. 2 (a), a schematic diagram of a rear group structure of the present utility model is shown, wherein a first aspheric positive lens 111 is located at the leftmost side of the lens group, and is close to the chip 101, and is a first aspheric positive lens of a refractive system, and a first spherical positive lens 112, a second spherical negative lens 113 and a third spherical positive lens 114 are cemented into a three cemented lens with a contour shape of two sides protruding.

In the rear group, the light beams of each view field on the surface of the first aspheric positive lens 111 are relatively dispersed, the overlapping area is less than that of other lenses in the group, and when the aspheric surface type is used, the light angles and aberration of different view fields can be corrected more favorably, so that the system keeps an object space telecentric state, and the brightness is improved.

The three-cemented lens formed by the first spherical positive lens 112, the second spherical negative lens 113 and the third spherical positive lens 114 plays a key role in correcting chromatic aberration and secondary spectrum, and the chromatic aberration, the coma aberration and the astigmatism are mainly corrected through the cemented surface.

Referring to fig. 2 (b), for the structure of the focusing group according to the present utility model, the overall focal power of the focusing group is approximately zero and is in the range of 0-0.01, the focusing group 120 can realize clear focusing of the projection image by moving axially under different projection distances, and the positive and negative separating lenses of the focusing group almost do not generate an impression on the central view field during moving, but as the aperture increases, the incident angle of the light ray on the lens surface starts to increase gradually, so that the aberration variation of the aperture edge is relatively severe, and the subtle aberration variation brought by different projection distances can be compatible by the light angle difference of the lower view field and the edge view field.

Referring to fig. 2 (c), a schematic diagram of a front group structure of the present utility model is shown, in which a sixth spherical positive lens 131 and a seventh spherical positive lens 132 form a front group positive lens group, an eighth spherical negative lens 133, a ninth spherical negative lens 134 and a second aspherical negative lens 135 form a front group negative lens group, and at least one positive lens refractive index is required to be greater than 1.83 in the positive lens group due to the requirement of bearing optical power, but the other lens material is a medium refractive index and a medium abbe number in consideration of balance of other aberrations, and the curvature of the lens surface is adjusted by adjusting the refractive index, so as to generate appropriate high-order aberrations.

The ninth spherical negative lens 134 in the negative lens group is made of a material with a low refractive index and a high abbe number, mainly for reducing the introduction of chromatic aberration, and the matching combination of the positive lens group and the negative lens group can effectively correct curvature of field and achieve the effect of field flattening.

The second aspheric negative lens has a large caliber, and the light beams of each field of view are dispersed on the lens surface by the large caliber, so that aspheric coefficients can be easily adjusted for different aperture bands to adapt to aberration correction requirements of different fields of view.

The optical parameter values of the above design examples are shown in table 1 below, and the equation of the above aspherical curve is as follows:

in the formula, c is the curvature corresponding to the radius, y is the radial coordinate, the unit is the same as the length unit of the lens, k is the conical coefficient, and r ₂ ～r ₁₆ The coefficients corresponding to the radial coordinates are respectively represented.

Fig. 5 (a) and fig. 5 (b) are graphs of vertical axis chromatic aberration at the screen when projected images of 81 inches and 238 inches are respectively at 20 ℃, the vertical axis chromatic aberration describes the difference of the principal rays of different light waves at each view field position in the height direction at the image plane, the smaller the difference is, the smaller the chromatic aberration of the system is, the better the imaging quality is, the pixel size is 937um when projected image size of 81 inches is, the pixel size is 2744um when projected image size of 238 inches is, and the transverse chromatic aberration at each position can be seen to be no more than 0.6 pixel at each object plane height, and the characteristic of low transverse chromatic aberration is realized.

Fig. 6 (a) and fig. 6 (b) are respectively a horizontal fan graph at the screen when the images are projected at 20 ℃ by 81 inches and 238 inches, the abscissa represents the normalized entrance pupil, the ordinate is the value of the light deviated from the principal ray at the image plane, the horizontal axis is the scale of fig. 6 (a) being +/-2000 um, the scale of fig. 6 (b) being +/-4000 um, the curves of the small aperture and the medium aperture are relatively close to the horizontal axis, the imaging quality is good, the light of the edge aperture is relatively divergent, the splicing gap between the pixels of the chip can be softened to a certain extent, and the granular sensation during viewing is reduced.

Fig. 7 (a) and 7 (b) are MTF diagrams at the screen at an ambient temperature of 20 ℃ and 50 ℃ on an 81-inch projection screen, the MTF observation line pair is 0.537lp/mm on an 81-inch projection screen, the MTF diagrams represent the comprehensive resolving power of the optical system, and the horizontal axis in the diagrams represents the spatial frequency in units: the number of turns per millimeter (cycles/mm), the vertical axis represents the value of Modulation Transfer Function (MTF), the value of MTF is used for evaluating the imaging quality of a lens, the higher the MTF curve is, the straighter the imaging quality of the lens is, the stronger the reduction capability of a real image is, the better the superposition degree of the curves of each view field is, the better the consistency of the image quality is, as can be seen from fig. 7 (a) and fig. 7 (b), when the ambient temperature is 20 ℃ and 50 ℃, the MTF of the whole view field is more than or equal to 0.5 and the image quality is good when the spatial frequency of the visible light wave band is 0.537 lp/mm.

FIGS. 8 (a) and 8 (b) are, respectively, MTF plots at the screen at ambient temperatures of 20℃and 50℃for a 238 inch projection screen, with an MTF observation line pair of 0.183lp/mm for a 238 inch projection screen; as can be seen from FIG. 8 (a) and FIG. 8 (b), the MTF of the full field of view is more than or equal to 0.5 when the spatial frequency of the visible light wave band is 0.183lp/mm at the ambient temperature of 20 ℃ and 50 ℃, and the image quality is good.

The following cases are ultra-short focal projection lenses suitable for a 0.47 inch DMD, with a throw ratio tr=0.5, OFFSET offset=100%, f# =1.7, and their actual design parameters are referenced in tables 1-2

Table 1:

table 2:

finally, it should be noted that: the foregoing description is only a preferred embodiment of the present utility model, and the present utility model is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present utility model has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the protection scope of the present utility model.

Claims (6)

1. The utility model provides a wide angle short burnt projection lens, includes back group, focuses group and preceding group triplex, its characterized in that:

the rear group at least comprises an aspheric lens and a cemented lens;

the focusing group at least comprises a group of positive and negative lenses;

the front group includes a positive lens group and a negative lens group of large optical power.

2. The wide-angle short-focus projection lens of claim 1, wherein:

the rear group of aspheric lenses are the first lens closest to the prism, and the cemented lenses are three cemented lenses and are close to the diaphragm;

the negative lens in the focusing group is close to the diaphragm;

the front group of positive lens group with large focal power is composed of a plurality of positive lenses, the negative lens group is composed of a plurality of negative lenses, the positive lens group is close to the focusing group, and the negative lens group is close to the projection surface.

3. The wide-angle short-focus projection lens of claim 1, wherein:

in the rear group three cemented lens, the positive and negative distribution of the lens is: positive-negative-positive, wherein the negative lens is made of a material with a high refractive index Nd being more than or equal to 1.83 and a low Abbe number Vd being less than or equal to 40, and the positive lens is made of a material with a low refractive index Nd being less than or equal to 1.50 and a high Abbe number Vd being more than or equal to 70;

at least one lens in the front group positive lens group is made of material with high refractive index Nd being more than or equal to 1.83, and at least one lens in the negative lens group is made of material with high Abbe number Vd being more than or equal to 70.

4. The wide-angle short-focus projection lens of claim 1, wherein:

the whole focal group has weaker focal power, and the absolute value of the focal power is in the range of 0-0.01;

the front group positive lens group has stronger combined focal power, and the absolute value of the focal power is larger than 0.03;

the front group negative lens group has strong combined focal power, and the absolute value of the focal power is larger than 0.1.

5. The wide-angle short-focus projection lens of claim 2, wherein:

the outline of the three cemented lenses in the rear group is a drum-shaped lens with two convex sides;

the outline of the positive lens in the focusing group is a meniscus lens;

the front group positive lens group is provided with at least one biconvex positive lens, the negative lens group is provided with at least one biconcave negative lens and one meniscus negative lens, and the meniscus negative lens is close to the projection surface.

6. The wide-angle short-focus projection lens of any one of claims 1-5, wherein:

the rear group comprises, in order from the object side to the image side: the lens comprises a first aspheric positive lens, and a triple cemented lens formed by a first spherical positive lens, a second spherical negative lens and a third spherical positive lens;

the focusing group includes: a diaphragm aperture, a fourth spherical negative lens and a fifth spherical positive lens;

the front group includes: a sixth spherical positive lens, a seventh spherical positive lens, an eighth spherical negative lens, a ninth spherical negative lens, and a second aspherical negative lens.